ARC – adaptive replacement cache …
well there is no dedicated readzilla (L2-ARC) or logzilla (ZIL) for my test SAN (NexentaStor)
i was curios to see the dataset of ARC content and ended up with this script,
admin@nssan:~$ ./arc_summary.pl
System Memory:
Physical RAM: 8173 MB
Free Memory : 770 MB
LotsFree: 127 MB
ZFS Tunables (/etc/system):
ARC Size:
Current Size: 5613 MB (arcsize)
Target Size (Adaptive): 5613 MB (c)
Min Size (Hard Limit): 893 MB (zfs_arc_min)
Max Size (Hard Limit): 7149 MB (zfs_arc_max)
ARC Size Breakdown:
Most Recently Used Cache Size: 44% 2497 MB (p)
Most Frequently Used Cache Size: 55% 3116 MB (c-p)
ARC Efficency:
Cache Access Total: 5292249
Cache Hit Ratio: 96% 5110509 [Defined State for buffer]
Cache Miss Ratio: 3% 181740 [Undefined State for Buffer]
REAL Hit Ratio: 93% 4939551 [MRU/MFU Hits Only]
Data Demand Efficiency: 97%
Data Prefetch Efficiency: 62%
CACHE HITS BY CACHE LIST:
Anon: 1% 97516 [ New Customer, First Cache Hit ]
Most Recently Used: 14% 716979 (mru) [ Return Customer ]
Most Frequently Used: 82% 4222572 (mfu) [ Frequent Customer ]
Most Recently Used Ghost: 0% 11400 (mru_ghost) [ Return Customer Evicted, Now Back ]
Most Frequently Used Ghost: 1% 62042 (mfu_ghost) [ Frequent Customer Evicted, Now Back ]
CACHE HITS BY DATA TYPE:
Demand Data: 52% 2706672
Prefetch Data: 1% 95218
Demand Metadata: 43% 2198797
Prefetch Metadata: 2% 109822
CACHE MISSES BY DATA TYPE:
Demand Data: 31% 57731
Prefetch Data: 31% 57053
Demand Metadata: 33% 60038
Prefetch Metadata: 3% 6918
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